The present invention relates to a temperature sensor having a resistance value which changes in response to a temperature change and electronic equipment employing the sensor.
In recent years, the use of thermistors and temperature sensors the resistance value of which suddenly increases at a specific temperature has been increasing in circuits of electronic equipment such as personal computers for the purpose of preventing an overcurrent condition. Similar temperature sensors are also used for the prevention of overheating damage due to short circuits in secondary batteries. As one of these temperature sensors for applications requiring a small and chip-shaped configuration for incorporation into a small electronic equipment, a temperature sensor employing a carbon-polyethylene composite as disclosed in U.S. Pat. No. 4,238,812 has been put into practical use.
When carbon is used as electrically conductive particles, application to a power supply circuit that requires a large current has been difficult because of its high specific resistance as compared with metals, and a sensor with a lower resistance value has been desired.
In addition, there has been a demand for a simple-to-manufacture, highly reliable, and low cost sensor.
To address the above foregoing issues, the present invention provides a temperature sensor having a low specific resistance, high reliability, and a low cost, and an electronic equipment using the temperature sensor.
The temperature sensor of the present invention includes a temperature sensitive layer in which an electrically conductive powder is suspended in a mixture of a resin obtained by copolymerizing a flexible monomer, a hydrophobic monomer, and a monomer having a glycidyl radical, and a hardening agent.
The temperature sensor of the present invention employs tetrahydrofurfuryl acrylate or methacrylate as the above-mentioned flexible monomer. Also, as the hydrophobic monomer, fluorine-containing acrylate or methacrylate is employed. Furthermore, it uses glycidyl acrylate or glycidyl methacrylate as the monomer having a glycidyl radical. As the hardening agent to harden the above copolymerized resin by heating, a hardening agent for epoxy resin is used. Also, as the electrically conductive powder to be suspended in the mixture of the above hardening agent, a metal powder is preferable. The preferable particle size of the electrically conductive powder is in the range of 1 to 10 xcexcm.
By employing the above configuration, the temperature sensor in accordance with the present invention can be manufactured by a simple method of coating paint suspended with an electrically conductive powder on a substrate and subsequently hardening by heating. Also, the present invention provides a temperature sensor having a low resistance, superior temperature sensitivity, high reliability yet with a low cost. Furthermore, the temperature sensor of the present invention is suitable for miniaturization and implementation into chips lending itself to applications in a small electronic equipment.
In addition, the electronic equipment which uses the temperature sensor of the present invention can be made small, and its electronic circuit can be protected by a sudden increase of resistance value at a specific temperature.